Materiales y materias primas: Madera.

What is Wood and Its Historical Significance?

Historical Uses of Wood

• Wood has been utilized since ancient times as both fuel and construction material, evident in prehistoric spears, tools, wheels, Viking ships, Egyptian sculptures, religious images, railway sleepers, temples, palaces, homes, bridges, and furniture.

• It plays a crucial role in various industries and the production of numerous objects.

Composition and Properties of Wood

• The cellulose derived from wood constitutes 95% of global paper production. Water is a primary component of green wood; lignin is also significant for veterinary pharmaceuticals and biodegradable plastics.

• Wood is defined as a biological material from plants that forms the solid part of trees and shrubs beneath the bark. It can be sourced from trunks as well as branches and roots.

How Is Wood Processed and Utilized?

Forms of Wood Usage

• Trunk wood can be processed into sheets or boards for construction or carpentry. Chemical industries utilize it for cellulose extraction along with other products like nitrocellulose.

• Branches and roots are used for fine carpentry or ground to extract resins or create regional medicines.

Functions Within Trees

• In trees, wood serves structural support while transporting water and nutrients from the soil to leaves. The trunk supports branches forming the canopy while storing reserve substances.

Cultural Significance of Trees

Symbolism Across Cultures

• An ancient Eastern legend suggests that trees are born at the same rate as humans. Various cultures associate trees with birth and life cycles.

• This symbolism often predates their practical value as natural resources.

Forests: Natural vs. Man-Made

Forest Formation

• Trees can grow individually or collectively to form forests which maintain self-regulated conditions over time.

• Human-generated forests may consist of native or exotic species aimed at economic or environmental goals.

Sustainable Forestry Practices

• Legislation aims to replace unplanned extraction practices with sustainable forestry management that minimizes environmental impact while ensuring economic viability over time.

Types of Wood: Characteristics & Applications

Durability Considerations

• Different types of wood have specific uses; untreated pine or poplar would decay quickly when exposed to water.

• Conversely, some woods like oak remain intact underwater for centuries; technology now allows less durable woods to be treated for similar longevity.

Growth Dynamics in Trees

Growth Phases

• Tree growth occurs primarily during spring through autumn; winter months see reduced growth rates.

• Primary growth starts at shoot tips where meristematic cells divide continuously before elongating into woody structures.

Secondary Growth Mechanisms

• Secondary growth involves a thin cylindrical layer around the tree trunk producing bark outwardly while generating new wood inwardly through three cell types essential for thickening processes.

Anatomy of Tree Structure

Internal Composition

• Newer wood layers form towards the center with minimal water transport activity; they mainly provide structural support.

Bark Functionality

• The outer bark protects the tree made up mostly by dead tissue (cork), while inner bark (phloem/liver tissue), distributes photosynthesis products throughout the tree's structure.

Sapwood vs Heartwood

Understanding Wood: Composition and Properties

Structure and Composition of Wood

• The heartwood, which is physiologically dead and provides structural support, tends to be darker due to the accumulation of essential oils, gums, resins, tannins, and other substances that color the wood.

• Wood consists primarily of cellulose (50%), lignin (30%), and various organic compounds (20%) such as starches, sugars, fats, tannins, essential oils, minerals, dyes, waxes, and resins.

Acoustic Properties of Wood

• In orchestras, "wood" refers to a group of instruments; however, not all are made from wood. The quality of sound in instruments like pianos is significantly influenced by a thin wooden piece called the soundboard.

• Due to its elastic nature, wood resonates with sound waves—this property makes it ideal for instrument manufacturing and concert hall acoustics.

Physical Properties of Wood

• When dried properly, wood serves as an excellent thermal insulator. Its natural shine and design contribute to its economic value.

• Different types of wood exhibit varying densities; dense woods include quebracho and lapacho while lighter options include pine and cedar.

Homogeneity and Plasticity in Wood

• Homogeneous wood has uniform fiber structure across its surfaces; for example, pines are more homogeneous compared to less uniform woods like beech.

• A plastic wood can bend without returning to its original shape once the force causing the flexion is removed; beyond a certain point of plasticity leads to breakage.

Insulation Properties

• Woods like lapacho or incense are favored for flooring due to their hardness. Eucalyptus and beech are preferred for sports equipment because of their elasticity.

Resistance Characteristics

Hardness

• Hardness refers to resistance against penetration or abrasion; yellow mora and lapacho are commonly used for flooring due to this characteristic.

Strength Against External Forces

• Resistance against external forces includes tensile strength (resistance before tearing), crucial for outdoor elements like columns. Compression resistance is vital in architecture for supporting structures.

Flexural Strength

• Flexural strength measures how well thin pieces resist breaking under load outside their supports—important in shelves or benches.

Shear Resistance

• Shear resistance pertains to how well wood withstands cutting forces during processes like sawing or planing; cedar is noted for good cutting performance.

Buckling Resistance

• Buckling occurs in slender pieces under strong longitudinal compression; if uncorrected loads lead these pieces toward deformation or breakage.

Splitting Resistance

Understanding Wood Properties and Their Applications

Elasticity of Wood

• Elasticity is defined as the ability of wood to return to its original dimensions after being subjected to compressive load. Eucalyptus and ash are noted for their high elasticity, making them suitable for sports equipment like hockey sticks and cricket bats.

Color Variations in Wood

• Wood can exhibit a range of natural colors including white, green, gray, yellow, and black, influenced by various factors.

• The color spectrum ranges from the white of guatambú to the black of guayúvira. Yellow tones are common in pines and other species while greens and grays are rarer.

Organoleptic Properties

• Aroma is an important characteristic that can determine the desirability of wood; some woods have pleasant scents while others may be rejected due to unpleasant odors.

• Freshly cut wood emits strong odors due to the evaporation of oils and resins. Some woods like incense have distinctive aromas that enhance their appeal.

Environmental Influence on Wood Behavior

• Different types of wood behave differently under varying environmental conditions; for instance, a door made from identical materials will perform differently in different climates due to moisture levels.

• Wood's organic nature makes it susceptible to decomposition and dimensional instability when exposed to humidity changes.

Durability Factors

• The durability of wood varies with environmental conditions; some woods like oak can withstand high humidity while others deteriorate quickly.

Technological Advances in Wood Processing

Impact of World War II on Wood Industry

• WWII significantly affected all material industries including wood; prior to the war, wood was being replaced by other materials but demand surged during wartime construction efforts.

Mechanical Transformation Processes

• Technological advancements improved wood processing techniques such as sawing which optimizes time and energy use during production.

Types of Saws Used in Processing

• Circular saws come in various forms (simple, double, multiple), each serving different functions within the cutting process.

Efficiency Comparisons Among Saw Types

Wood Cutting Techniques and Their Implications

Overview of Wood Cutting Methods

• A wide range of modern wood cutting systems exists, surpassing traditional methods. The simplest method involves cutting along growth rings and wood rays, known as tangential cutting.

• Radial cutting aligns the cut with a wood ray, intersecting the growth rings; this method is typically used for special orders.

• Cutting can also occur in planes parallel to the bark, producing uniform thin pieces. This technique is recommended when mechanical strength is crucial.

• Simultaneous cuts involve making multiple longitudinal cuts at once, typical of multiple alternative saws, yielding several pieces in one operation.

Bark Removal Process

• Bark removal resembles peeling an apple and is essential for certain uses while optional for others.

• Bark can be removed manually or mechanically and is necessary for wood intended for industrial preservation or pulp production.

• Removed bark can serve as fuel. While not essential in sawmills, it offers advantages like improving cutter longevity by eliminating harmful materials like sand or small stones.

• Removing bark helps control insect development that affects green wood and allows utilizing trunk sides as raw material for cellulose production.

Drying Wood: Importance and Benefits

• Wood drying eliminates moisture, which can account for one-third to half of its total weight. Both drying and bark removal may have unexpected effects on saw blades and insect development.

• Green wood may be used in construction (e.g., scaffolding), but drying enhances stability against dimensional changes due to humidity variations and improves strength properties.

• Dried wood behaves better during planing, glue application, painting processes, and increases resistance to various insects. It’s typically stored stacked and bundled with plastic tape to prevent disassembly or contamination before exportation.

Energy Considerations in Wood Usage

• Using wood contributes to energy savings but can also lead to waste depending on its applications. The energy required for producing wood is negligible since trees utilize solar energy during growth compared to other materials like steel or aluminum.

• For every ton of wood produced, 430 kilowatt-hours are consumed; this contrasts sharply with 2700 kWh per ton of steel and 17000 kWh per ton of aluminum.

Environmental Impact of Wood Harvesting

• Forest ecosystems are suffering from inefficient burning practices where most harvested wood (13% of global energy use today) is wasted through ineffective heating methods in poorer regions.

• Deforestation occurs not only from logging but also from land clearing for agriculture. Sustainable harvesting could yield more profit without destroying forests than current dominant practices that severely harm the environment.

Reflection on Material Alternatives